Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

A source-modulation microwave spectrograph was utilized to measure line width parameters for several spectral lines in the pure rotational spectrum of formaldehyde (H₂CO). The spectrograph featured high-gain ac amplification and phase-sensitive detection, and was capable of measuring microwave lines having absorption coefficients as small as 10⁻⁷ cm⁻¹ with a frequency resolution on the order of 30 kHz. Center frequencies of the measured lines varied from 4,830 MHz to 72,838 MHz; hence, most of the observations were made on transitions between K-doublets in the rotational spectrum. Corrections were applied to the measured line width parameters to account for Doppler broadening and, where possible, for deviations due to magnetic hyperfine structure in some of the K-doubled lines. Low modulation voltages and low microwave power levels were used to minimize modulation and saturation broadenings; other extraneous broadenings were found to be insignificant. The primary broadening mechanism at low gas pressure is pressure broadening, and a review of this topic is included. Line width parameters for the several observed transitions were determined by graphing half-widths versus pressure for each spectral line, and performing a linear least-squares fit to the data points. Repeatability measurements indicated the accuracy of the line width parameters to be better than ±10 percent. The reasons for this repeatability spread are discussed, Broadening of each line was measured for self- and foreign-gas broadening by atomic helium and diatomic hydrogen. Effective collision diameters were calculated for each broadening interaction, based on the observed rates of broadening.

Recent photometric studies have revealed that surface spots that produce flux variations are present on virtually all L and T dwarfs. Their likely magnetic or dusty nature has been a much-debated problem, the resolution to which has been hindered by paucity of diagnostic multi-wavelength observations. To test for a correlation between magnetic activity and photometric variability, we searched for Ha emission among eight L3-T2 ultra-cool dwarfs with extensive previous photometric monitoring, some of which are known to be variable at 3.6 mu m or 4.5 mu m. We detected Ha only in the non-variable T2 dwarf 2MASS J12545393-0122474. The remaining seven objects do not show Ha emission, even though six of them are known to vary photometrically. Combining our results with those for 86 other L and T dwarfs from the literature show that the detection rate of Ha emission is very high (94%) for spectral types between L0 and L3.5 and much smaller (20%) for spectral types. >= L4, while the detection rate of photometric variability is approximately constant (30%-55%) from L0 to T8 dwarfs. We conclude that chromospheric activity, as evidenced by H alpha emission, and large-amplitude photometric variability are not correlated. Consequently, dust clouds are the dominant driver of the observed variability of ultra-cool dwarfs at spectral types, at least as early as L0.

Study of structural and particularly dynamical properties of the interface of water with graphite and rutile surfaces points towards anomalous behavior of water molecules close to solid matter. Evaluation of statistical properties like translational and rotational diffusivity, residence times and autocorrelation functions of orientation vectors indicates that the translation and rotation of water molecules can be not only hindered, but also facilitated, according to the particular local density, interactions and and geometrical structure of the surface. The newly developed methods for the measurement of statistical rotational properties near to liquid-solid boundary overcomes the difficulties that are closely related to the measurement of dynamical properties in strongly inhomogeneous environment in a way, that can be applied to other model systems of this type.

Thesis is focused on study of phlebotomus generative attributes development and body dimension influence for some determinant notes therefore is divided into two thema parts. First thematic part of thesis is heeding to rotation of outer genitalia of chosen phlebotomus subgenus males and their representatives: Adlerius (Phlebotomus arabicus), Larroussius (Phlebotomus orientalis and Phlebotomus tobbi), Euphlebotomus (Phlebotomus argentipes), Paraphlebotomus (Phlebotomus sergenti), Phlebotomus (Phlebotomus papatasi), Lutzomyia (Lutzomyia longipalpis) and Sergentomyia (Sergentomyia schwetzi). In this parts was discovered and compared time of station of genitalia for chosen subgenera. Also the time from emergence of adults to rotation and rotation time dependence on adults daytime eclosion was measured. Times of rotation time duration including that of times from rotation beggining were at subgenuses expressively different, from S. schwetzi with the shortest rotation time of 12 hours to P. sergenti with the longest with average time rotation of 32 hours. Further were compared rotations of two genuses within subgenus Larroussius: P. orientalis a P. tobbi. Here also were each rotation times expressively different that do not validate the rotation should be specific for given subgenus. Observed was also...

Pour caractériser la mobilité moléculaire au sein de structures complexes, la relaxométrie RMN consiste à déterminer les temps de relaxation dans une gamme de fréquence aussi large que possible et notamment à très basse fréquence où se manifestent les mouvements lents. L'évolution de la vitesse de relaxation longitudinale R1 (qui correspond à l'inverse du temps de relaxation longitudinale T1) en fonction de la fréquence de mesure conduit à ce que l'on appelle une courbe de dispersion. Les travaux présentés dans cette thèse sont entièrement dédiés à cette technique que nous avons décidé d'appliquer à l'étude de fluides introduits à l'intérieur de milieux poreux et ceci constitue une première au laboratoire. Les systèmes ayant servi de support à cette étude sont de nature très différente puisqu'ils concernent 1) des matériaux mésoporeux silicatés qui ont été hydratés dans le but d'étudier le comportement des molécules d'eau introduites à l'intérieur du matériau et 2) des organogels formés dans le toluène pour lesquels nous avons mené une étude du comportement dynamique du solvant à l'issue du processus de gélification. Pour caractériser au mieux la dynamique des fluides à l'intérieur de ces systèmes, des méthodes expérimentales originales, nécessitant l'utilisation de plusieurs instruments, ont été développées, permettant ainsi d'obtenir des courbes de dispersion allant de 0 à 400 MHz. Grâce à des développements méthodologiques et théoriques, nous avons été capables d'identifier les différents mécanismes de relaxation à l'origine de ces courbes de dispersion et de donner une signification physique aux paramètres issus de cette interprétation / In order to characterize molecular mobility within complex structures, NMR relaxometry aims at the determination of relaxation times in a frequency range as large as possible and in particular at very low frequencies where slow motions can be revealed. The evolution of the longitudinal relaxation rate R1 (which corresponds to the inverse of the longitudinal relaxation time T1) as a function of the measurement frequency leads to so-called dispersion curves. The work presented in this thesis is, for the first time in this laboratory, entirely dedicated to this technique, applied to the study of fluids within porous media. The systems investigated are very different; they include 1) hydrated mesoporous materials for which different states of water molecules were distinguished and 2) organogels formed in toluene, the dynamical behavior of which being studied subsequently to the gelation process. Original experimental methods, involving the use of several instruments, were developed, allowing us to obtain dispersion curves between 0 and 400 MHz. Thanks to methodological and theoretical developments, we were able to identify the different relaxation mechanisms and able to give a physical meaning to the parameters resulting from the fitting of dispersion curves

The purpose of this study was to investigate the Willingness to Pay (WTP) of conserving a ten hectares forest area in Rutvik, amongst the population of Luleå municipality. Furthermore, the study investigated the factors influencing the WTP and its impact on a Faustmann-Hartman rotation period. The tested influential factors were both socio-economic and attitudes towards use values and non-use vales that a forest stand can provide the society. The study used an empirical approach, were a survey was created using a Contingent Valuation Method (CVM). The survey consisted of three parts, where the first part asked the respondents general questions, the second part let the respondent rate different type of forest values and finally a last part where an open-ended question asked the respondents of their maximum WTP. The results indicated that the mean WTP was equal to 15.9 SEK for the total forest area. The results also demonstrated that income had a significant positive impact on WTP and that living nearer the targeted forest gave a higher probability of having a WTP. The only service that indicated significant result was altruistic values, which value had a positive impact on the WTP. It also indicated that the researched WTP extended the traditional Faustmann rotation formula from 56 to 58 years for pine and 75 to 78 years for spruce.

Zeolites are crystalline microporous aluminosilicates with well-defined cavities or channels of molecular dimensions. They are widely used for applications such as gas adsorption, gas storage, ion exchange and catalysis. The size of the pore opening allows zeolites to be categorized into small, medium, large and extra-large pore zeolites. A typical zeolite is the small pore silicoaluminophosphate SAPO-34, which is an important catalyst in the MTO (methanol-to-olefin) process. The properties of zeolite catalysts are determined mainly by their structures, and it is therefore important to know the structures of these materials in order to understand their properties and explore new applications. Single crystal X-ray diffraction has been the main technique used to determine the structures of unknown crystalline materials such as zeolites. This technique, however, can be used only if crystals larger than several micrometres are available. Powder X-ray diffraction (PXRD) is an alternative technique to determine the structures if only small crystals are available. However, peak overlap, poor crystallinity and the presence of impurities hinder the solution of structures from PXRD data. Electron crystallography can overcome these problems. We have developed a new method, which we have called “rotation electron diffraction” (RED), for the automated collection and processing of three-dimensional electron diffraction data. This thesis describes how the RED method has been applied to determine the structures of several zeolites and zeolite-related materials. These include two interlayer expanded silicates (COE-3 and COE-4), a new layered zeolitic fluoroaluminophosphate (EMM-9), a new borosilicate (EMM-26), and an aluminosilicate (ZSM-25). We have developed a new approach based on strong reflections, and used it to determine the structure of ZSM-25, and to predict the structures of a series of complex zeolites in the RHO family. We propose a new structural principle that describes a series of structurally related zeolites known as “embedded isoreticular zeolite structures”, which have expanding unit cells. The thesis also summarizes several common structural features of zeolites in the Database of Zeolite Structures. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript.</p>

Bakgrund: I Sverige finns lagstiftning kring att publika och privata aktiebolag ska genomgå revision. Syftet med revision är att granska ett bolags räkenskaper och den förvaltning som sker av styrelse och verkställande direktör. I ämbetet som revisor ska denne agera oberoende gentemot bolaget och just oberoendet ifrågasattes av EU-kommissionen efter den finanskris som bland annat drabbade Europa mellan 2007 och 2009. Ifrågasättandet ledde till en ny lag för publika aktiebolag som tvingar dem att byta revisionsbyrå. Genomförandet av en byrårotation kan för både privata och publika aktiebolag ske frivilligt eller ofrivilligt. Enstaka studier har tidigare undersökt området byrårotation med en kvalitativ ansats, vilket delvis motiverar studiens syfte.    Syfte: Syftet med studien är att undersöka vad som är av betydelse då ett företag byter och väljer ny revisionsbyrå, och om det skiljer sig åt mellan publika och privata aktiebolag. Genom studien vill författarna bidra till en ökad förståelse för vad som ligger till grund för de ageranden och val företagen gör gällande byrårotation.    Metod: För att skapa en djupare kunskap om hur företag resonerar vid en byrårotation har ett abduktivt tillvägagångssätt tillämpats. Inledningsvis har tidigare forskning studerats för att skapa en bild av vad som tidigare konstaterats varit av betydelse för företag vid deras byte av respektive val av ny revisionsbyrå. Tre huvudsakliga kategorier kommer fram i form av företagets egenskaper, revisorns egenskaper och själva revisionen. Därefter har intervjuer med sex företag genomförts som legat till grund för uppkomsten av teori i form av två nya faktorer.   Slutsats: Den tydligaste skillnaden som går att utröna mellan publika och privata aktiebolag i denna studie är att vid en byrårotation ser privata aktiebolag i större grad relationen till revisorn som viktig, och publika aktiebolag lägger större vikt vid revisorns kompetens. Studien visar även att det är en kombination av olika faktorer har betydelse vid processen av en byrårotation och inte en enskild sådan. Alla fallföretag har haft unika processer vid byrårotationen. Vidare har två nya faktorer påträffats i form av lagen om obligatorisk byrårotations påverkan på företagen, och vilken betydelse beslutsfattarnas erfarenhet har på byrårotationen. Intervjuer med representanter för företagen har även möjliggjort nya förklaringar av vissa begrepp. / Background: Legislation in Sweden force listed and private companies to undergo an audit with the purpose to examine the books of the company and the management of the board and the chief executive officer. The auditor must act independently of the company being audited. The matter of independence has been questioned by the European Commission following the financial crisis that struck the world economy in 2007 to 2009. This questioning resulted in a new law regarding listed companies, forcing them to undergo an audit firm rotation. Both listed and private companies can do either a voluntary or non-voluntary audit firm rotation. Occasional studies have investigated the matter of audit firm rotation with a qualitative approach, which partly motivates the purpose of this study.     Purpose: The purpose of this study is to investigate what could be of importance when a company switches to a new audit firm, and if this differs between listed and private companies. By means of this study the authors want to contribute with an enhanced understanding on what basis the companies make their acts and choices regarding audit firm rotation.     Method: An abductive approach has been used to create a profound knowledge regarding how companies reason about an audit firm rotation. Earlier research has been studied to create an image of what aspects that earlier have been of importance  to companies in their decision to switch and choose a new audit firm. Three main categories arise, the company characteristics, the auditors characteristics and the audit itself. Thereafter interviews have been conducted with six companies which have been the foundation for new theory as two new factors.       Conclusion:The most distinct difference between listed and private companies in this study is that listed companies regard the auditors competence as more important than the private companies do. The private companies values the relation to the auditor higher than the listed companies. This study shows that a combination of different factors is of importance in the process of an audit firm rotation and not only a single one. All of the companies had unique processes regarding the audit firm rotation. Two new factors have emerged concerning the regulation of mandatory audit firm rotation, and what affects the experience of the decision makers of the audit firm rotation has. Interviews with delegates of the company has enabled new explanations of certain concepts.

Ce travail concerne l’écoulement incompressible et stationnaire autour d’un cylindre semi-infini en rotation, et ses propriétés de stabilité linéaire. L’effet de la courbure et de la rotation sur la stabilité de cet écoulement est étudié de manière systématique. Avant d’étudier la stabilité, nous calculons d’abord l’écoulement de base. A grand nombre de Reynolds, une couche limite se développe le long du cylindre, ce qui permet d’utiliser l’approximation de couche limite des équations de Navier–Stokes. Ces équations dépendent de deux paramètres de contrôle sans dimension, le nombre de Reynolds (Re) et le taux de rotation (S), et sont résolues numériquement pour obtenir les profils de vitesse et de pression pour une large gamme des paramètres de contrôle. Une couche limite initialement mince s’épaissit avec la distance axiale; ainsi, son épaisseur devient comparable et finalement plus importante que le rayon du cylindre. Au-delà d’un certain taux de rotation, les effets centrifuges conduisent `a un jet de paroi le long d’une portion du cylindre. L’extension axiale de ce jet augmente avec le taux de rotation. L’intensité du jet augmente aussi avec S. Des analyses asymptotiques de l’écoulement à grande distance axiale et à fort taux de rotation sont aussi présentées. L’analyse de stabilité linéaire du précédent écoulement est effectuée dans l’approximation locale. Après une décomposition en modes normaux, les équations des perturbations sont transformées en un problème de valeur propre `a fréquence complexe (ω). Ce problème dépend de cinq paramètres sans dimension: Re, S, la distance axiale normalisée (Z), le nombre d’onde axial (α) et le nombre d’onde azimutal (m). Les équations de stabilité sont résolues numériquement pour étudier les régions instables dans l’espace des paramètres. On observe que de faibles taux de rotation ont un effet important sur la stabilité de l’écoulement. Cette forte déstabilisation est associée à la présence d’un mode quasi-marginal pour le cylindre fixe et qui devient instable pour de petites valeurs de S. Ce phénomène est confirmé par une analyse en perturbation `a petit S. Sans rotation, l’écoulement est stable pour tout Re < 1060, et pour Z > 0.81. Mais, en présence d’une faible rotation, l’instabilité n’est plus limitée par une valeur minimale de Re ou un seuil en Z. Les courbes critiques dans le plan (Z, Re) sont calculées pour une large gamme de S et les conséquences pour la stabilité de l’écoulement discutées. Enfin, un développement asymptotique pour le nombre de Reynolds critique est obtenu, valable aux grandes valeurs de Z. / This work concerns the steady, incompressible flow around a semi-infinite, rotating cylinder and its linear-stability properties. The effect of cylinder curvature and rotation on the stability of this flow is investigated in a systematic manner. Prior to studying its stability, we first compute the basic flow. At large Reynolds numbers, a boundary layer develops along the cylinder. The governing equations are obtained using a boundary-layer approximation to the Navier–Stokes equations. These equations contain two non-dimensional control parameters: the Reynolds number (Re) and the rotation rate (S), and are numerically solved to obtain the velocity and pressure profiles for a wide range of control parameters. The initially thin boundary layer grows in thickness with axial distance, becoming comparable and eventually larger than the cylinder radius. Above a threshold rotation rate, a centrifugal effect leads to the presence of a wall jet for a certain range of streamwise distances. This range widens as the rotation rate increases. Furthermore, the wall jet strengthens as S increases. Asymptotic analyses of the flow at large streamwise distances and at large rotation rates are presented. A linear stability analysis of the above flow is carried out using a local-flow approximation. Upon normal-mode decomposition, the perturbation equations are transformed to an eigenvalue problem in complex frequency (ω). The problem depends on five non-dimensional parameters: Re, S, scaled streamwise direction (Z), streamwise wavenumber (α) and azimuthal wavenumber m. The stability equations are numerically solved to investigate the unstable regions in parameter space. It is found that small amounts of rotation have strong effects on flow stability. Strong destabilization by small rotation is associated with the presence of a nearly neutral mode of the non-rotating cylinder, which becomes unstable at small S. This is further quantified using smallS perturbation theory. In the absence of rotation, the flow is stable for all Re below 1060, and for Z above 0.81. However, in the presence of small rotation, the instability becomes unconstrained by a minimum Re or a threshold in Z. The critical curves in the (Z, Re) plane are computed for a wide range of S and the consequences for stability of the flow described. Finally, a large-Z asymptotic expansion of the critical Reynolds number is obtained.